1. Field of the Invention
The present invention relates to a copying machine for printing data read by a one-dimensional image sensor on a thermosensitive sheet with a thermal printer.
2. Description of the Prior Art
Copying machines in most widespread use today employ the Carlson process for copying image data on plane paper. The electrophotographic copying machines of this type require a high-voltage power supply for charging a photosensitive drum. It would be difficult to produce a portable electrophotographic machine because of a high power consumption rate necessitated by a heater for fixing toner images. The copying machines which operate based on the Carlson process must be maintained or serviced periodically by supplying toner and cleaning the photosensitive drum, for example. Since these copying machines are generally heavy and large in size, they are incapable of copying characters written on a wall, for example. The copying machines require various components such as the photosensitive drum, a charger for charging the photosensitive drum, a driver unit for driving the photosensitive drum, and a driver unit for feeding sheets of copying paper, for example. Inasmuch as these parts are expensive in general, the electrophotographic copying machines are costly to manufacture and hence are inappropriate for personal use. Therefore, the inventors have tried to exploit a new copying machine which is operated by a small type of dry battery and is provided with a Charge Coupled Device of first dimension (hereinafter referred to CCD (The construction and operation of the CCD is disclosed in detail within the technical report of pages 108 to 111 issued in December 1974 at the International Electron Device Meeting of IEEE in the U.S.A.)) and a thermal printing head. By the way, it is to be noted that, in the case of operating the CCD and thermal head printer at the same time for making a copy, it is necessary to transport image information having a length of one line from the CCD while the thermal head printer is adapted to copy the one line onto the sheet of thermally sensitive copy paper. In other words, it is necessary to sense one line content of image information to be read by the CCD by every one dots at the same time for an interval of removing pulse signals from the head strobe to the final strobe within the thermal head printer. Also, it is to be noted that the thermal head printer is adapted to receive an effect on the printing quality of the copying machine by factors such as power source voltage, printing time (i.e., width of strobe pulse), reserving heat of the thermal head printer. In general, it is desired to adjust either the power source voltage or the strobe for keeping the printing quality constant, but, in the case of a small copying machine to be operated by a dry battery, it is desired to control the strobe pulse width in order to obtain good efficiency, and a time for the one line printing in the thermal head printer is changed by the power source voltage or reserving heat of the thermal head printer. If the power source voltage is changed, the voltage loaded on the printer is varied to change the shade of print, thereby to render to make the printing quality worse.